Organic field effect transistors (OFETs) comprise an organic semiconductor layer between and over a source electrode and at least one drain electrode, an organic insulating layer over the semiconductor layer and a gate electrode. The source, drain and gate electrodes can comprise metals or organic conductive polymers. Organic electrode materials are for example polyaniline and polypyrrole. For example, polythiophene is used as the semiconductor and polyvinylphenol is used as the insulator.
Structuring of the conductive electrode layers is required for the production of OFETs or other components of organic polymers. Structuring of the other layers is not absolutely necessary but can improve the efficiency and performance of the components consisting of organic polymers.
WO 02/25750 describes the production of electrodes or conductor tracks using a lithography process. In that case the conductive organic layer of doped polyaniline (PANI) or polyethylene dioxythiophene (PEDOT) is applied to the substrate, for example a film, over an area thereof, by application by means of a doctor, by being sprayed on, by spin coating or by screen printing. A thin layer of photoresist is applied thereto and exposed in structured configuration. Upon development the exposed polyaniline layer is deprotonised by the action of the developer and thus becomes non-conducting. The photoresist which has remained is dissolved with a solvent. Prior to or after that step, the non-conductive matrix of the organic layer is dissolved out with a non-basic solvent.
Alternatively it is also possible for the exposed regions to be oxidatively removed prior to dissolution of the photoresist by reactive etching.
WO 02/25750 also describes that a chemical compound which has a deprotonising effect is applied by printing to the areal functional polymer layer, for structuring purposes. The compound is preferably a base. Non-conducting regions are selectively removed by subsequent rinsing.
There is the disadvantage that the lithographic process only works for the material polyaniline. In addition, it is not known in the state of the art for roll material to be structured with lithographic processes. With other structuring processes, for example printing, the minimum possible distance between the source and drain electrodes is at least between 30 μm and 50 μm. However endeavours are made to achieve lengths of approximately 10 μm in order to increase the performance and efficiency of the OFET.
WO 02/47183 proposes introducing the functional polymer into recesses in a shaping layer, for structuring the conductive organic layer and the other layers in an OFET. The shaping layer comprises a different organic material with insulating properties, into which a punch is pressed. That material is for example an UV-hardenable or heat-hardenable lacquer which is applied to a substrate over the full surface area thereof. The lacquer is hardened by irradiation, for example by means of UV light, and recesses are then produced in the shaping layer. The functional polymer is then scraped into those recesses. That process makes it possible therefore to produce extremely fine structures with lateral dimensions in the region of 2-5 μm. The scraping method is also not material-specific, that is to say it is suitable for the structuring of all layers of an OFET. Besides polyaniline, other conductive or semiconducting organic materials such as for example polypyrrole, polythiophene or also polyvinylphenol can be scraped into the recesses and thus structured. In addition the viscosity range for the scraping operation is incomparably greater than for the printing operation so that the functional polymers can be left substantially in their consistency. In addition relatively thick layers in the range of up to 1 μm can be produced. It is further proposed that the process is used in a continuous rolling printing operation. In that case the band comprises a substrate material with a shaping polymer applied thereto, which can be an UV-hardenable lacquer but also a heat-hardenable lacquer. The recesses are initially embossed therein with a stamping roller and the shaping polymer is subjected to initial hardening by UV irradiation. The lacquer is finally hardened with an UV lamp arranged thereafter. The functional polymer is then scraped into the structured lacquer, with a doctor scraper.
DE 100 33 112 describes a process which takes off the functional polymer which has been introduced into the shaping mold by means of a tampon and then applies it to the substrate or layers which are already present.